"[DME] Oman was more expensive than [ICE] Brent at one point," said a crude trader.

The November ICE Brent futures contract traded in a range of US$80.51/b to US$80.60/b between 0829 and 0830 GMT, trading data showed.

Over the same period, the November DME Oman crude futures contract was trading in a range of US$80.72/b to US$81.42/b, at least 21 cents/b above the Brent price.

Crude oil traders in Asia said Oman crude experienced volatility in price levels on the back of low liquidity which can occur as the contract nears end-of-month expiry.

Buyers and sellers of Oman typically look to cover outstanding positions before the contract expires on the last trading day of the month, which would be September 28 for the November contract.

Oman was pegged at US$80.02/b on the DME as of 0830 GMT Monday, up from US$78.16/b at the same time Friday. The price for November ICE Brent futures was US$80.58/b as of 0830 GMT Monday, bringing the spread between Brent and Oman on Monday to 56 cents/b.

Brent itself has climbed from a settle of US$78.80/b on Friday, in response to various supply side concerns that emerged in the global crude oil markets over the weekend.

On Friday at 0830 GMT the spread between November ICE Brent and DME Oman futures was US$1.17/b, with Brent at US$79.33/b at 0830 GMT.

The DME is a popular avenue for sour crude market participants to bid or offer the crude grade in 1,000-barrel lots as a futures contract with the option for physical delivery.

Meanwhile, S&P Global Platts assessed November cash Dubai crude at US$78.44/b Monday, while November cash Oman was at US$79.25/b, bringing the difference between the two grades to 81 cents/b.

Together, Dubai and Oman are tracked closely by traders of Middle East sour crude grades and typically trade in close proximity to one another.